In a mobile transmit diversity system, a base station may send diversity feedback to a mobile communications device or mobile device in its network or vicinity. The diversity feedback may instruct the mobile device to transmit a diversity signal with certain diversity parameters, such as phase difference or relative power amplitude. A base station may limit the size of its feedback to a mobile device to save downlink bandwidth. For example, a codebook size limitation considered by the 3rd Generation Partnership Project (3GPP) is two bits. Such phase feedback may only have four codebook options to direct the mobile device's phase: 0, +90, 180, or −90, for example. However, it is difficult with such a coarse resolution to provide sufficient sensitivity for optimum diversity gain.